WO2004027883A1

WO2004027883A1 - Method for producing led bodies with the aid of a cross-sectional restriction

Info

Publication number: WO2004027883A1
Application number: PCT/DE2003/003060
Authority: WO
Inventors: Thomas Manth
Original assignee: G.L.I. Global Light Industries Gmbh
Priority date: 2002-09-16
Filing date: 2003-09-15
Publication date: 2004-04-01
Also published as: DE10393816D2; DE10242947A1; AU2003269827A1; DE10242947B4; DE10242947B8; US7241637B2; US20060051901A1; CN1682382A

Abstract

The invention relates to a method for producing light-conductive LED bodies from a free-flowing material by feeding the latter into a mould. According to said method, if the distance between the electrode plane and the feed point is greater than 35 % of the distance between the feed point and the side of the mould lying opposite said point, the volumetric flow of a free-flowing material is reduced by at least one cross-sectional restriction, above the feed point and below the chip plane on the side of the mould comprising the feed point. If, on the other hand, said former distance is less than or equal to 35 % of the latter distance, the reduction takes place on the side of the mould lying opposite the feed point. The invention provides a method for producing light-conductive LED bodies, in which the LED electronics remain undamaged by the conventional effects of the feed process.

Description

Process for manufacturing LED bodies using a cross-sectional constriction

Description:

A process for the manufacture of light-conducting LED bodies, from egg ^¬ NEM prior to the final solidification of the flowable material by introducing into a mold, wherein the LED body and at least individual at least one light-emitting chip two - comprises electrodes, and - electrically connected to the chip wherein the flowable material is injected between a bottom region of the mold and the chip at least approximately parallel to the plane of the chip and at least approximately normal to a plane formed by two electrodes between the electrodes.

DE 101 59 522 discloses such a method for producing light-emitting diodes. The light-emitting diode to be manufactured is a radial LED, the shape of which is filled by radial injection of flowable material. The material is normally injected beneath the chip into a surface spanned by the electrodes. In this method, the material filling the mold flows around the chip and the bond wire arranged above it from below. This process protects the bond wire to such an extent that it is no longer torn off by the inflowing material. However, it often happens that - seen from the direction of Material injection - in front of or behind the electrodes, the material introduced into the mold builds up on one side. As a result, the flow front, which flows predominantly on one side, can push the bonding wire to the side so strongly that it comes into contact with the cathode. When the LED is energized later, the component fails due to a short circuit.

The present invention is therefore based on the problem of developing a method for producing light-guiding LED bodies in which the LED electronics are not impaired in the usual performance of the known injection molding or casting processes.

This problem is solved with the features of the main claim. For this purpose, the volume flow of a flowable material is at a distance of the electrode level from the insertion point that is greater than 30% of the distance between the insertion point and the mold side of the mold opposite the insertion point - above the insertion point and below the chip level on the mold side of the insertion point is throttled by at least one cross-sectional constriction, while - at a distance that is less than or equal to 30% of this distance - the throttling takes place on the mold side opposite the insertion point.

With this method for producing a luminescent diode, a specific input location and direction in conjunction with a predetermined throttling of the material volume flow at a defined location Current condition created, which allows a controlled, uniform filling of the mold without any damage to the LED electronics. For throttling, a shaped element is arranged in the individual mold cavity opposite the electrode fence, which narrows the flow cross section between the front edge of the shaped element and the chip. Depending on the type of plastic, the geometric dimension of the molded element and its surface structure facing the volume flow may be specially selected. This is easy to handle when using interchangeable throttle valves that support the molded element.

Due to the shaped element, the inflowing material is throttled at least on one side in such a way that the flow fronts migrating from below to the chip on both sides of the electrodes contact and flow around the chip and the bonding wire almost simultaneously. The almost simultaneous sheathing of the bond wire stabilizes the bond wire in its pre-planned position.

The method can also be used on luminescent diodes with multiple chips and electrodes.

Further details of the invention emerge from the subclaims and the following description of several schematically illustrated exemplary embodiments.

Figure 1: LED shape with narrowing of the cross section over the

Injection site; Figure 2: LED shape with cross-sectional narrowing compared to

Injection point Figure 3: Side view of an LED in a mold with a retracted mold slide; Figure 4: Front view of the LED from Figure 3; Figure 5: Top view of an LED manufacturing network next to

Spray nozzles; Figure 6: Bottom view of the LED from Figure 1 with several

Parting lines. FIG. 7: side view of an LED in a mold with the slide element extended; Figure 8: Top view of Figure 7 largely without shape.

FIGS. 3 to 6 show an LED (10), the light-conducting body (20) of which is produced, for example, by injection molding in one injection step.

The LED (10) shown here has an LED body (20) theoretically divided into two zones (21, 41), cf. Figure 4. The lower zone (41) of the body (20) is a so-called electronics protection zone, while the upper zone (21) is referred to as the light guiding zone. Both zones are separated from each other by a fictitious parting line (39). The parting line (39) is only shown in dotted lines in FIG. 4.

The electronics protection zone (41) generally surrounds the electrical connections (1, 4) lying in one plane (19), the light-emitting chip (6), a bonding wire (2) and a reflector trough (5). The latter is part of the cathode (4), for example. The chip (6) is seated in the reflector trough (5). The chip (6) contacts the anode (1) via the bonding wire (2). The bonding wire (2) is preferably in a plane (19) which is spanned by the center lines of the electrodes (1, 4). The light guiding zone (21) located above the chip transports the light emitted by the chip (6) to the outer surface (14, 15) of the LED (10) with as little loss as possible. With regard to its spatial design, the LED body (20) of the exemplary embodiment consists of three geometrical bodies (11, 14, 15) placed one against the other. The lower geometric body (11) is at least approximately a straight cylinder with two at least approximately parallel end faces and, for example, two flat flats (12, 13). The flats (12, 13) are parallel to the LED longitudinal axis (18) and form a right angle with each other. A flattening (12) is parallel to the electrode plane (19) formed by the center lines of the electrodes (1, 4). The lower end face forms the so-called bottom area (42). A straight truncated cone (14) adjoins the upper end face and tapers away from the cylinder (11). A dome (15) sits on the truncated cone (14) as the third geometric body. In the LED longitudinal section there is, for example, a tangential transition between the spherical cap (15) and the truncated cone (14).

The larger end face diameter of the truncated cone (14) measures approximately 5 mm in the exemplary embodiment. It is called the base size. The taper of the truncated cone (14) is e.g. 20% of the basic size. The total height of the LED (10) corresponds to approx. 180% of the basic size. The height of the cylinder (11), which, as a flange-like collar, protrudes beyond the truncated cone with respect to its radius by approximately 10% of the basic size, measures approximately 30% of the basic size. The depth of the flats (12, 13) is approx. 8% of the basic size.

The area of the truncated cone (14) above the chip (6) and the spherical cap (15) form the main light-emitting surface.

For LED production, the electrodes (1, 4) are part of a flat, punched, so-called electrode fence (80). Within this fence, the electrodes (1, 4) are connected to one another continuously via webs (81). A fence (80) contains, for example, 32 electrodes for 16 LEDs (10). The minimum distance the LEDs (10) integrated side by side in the fence (80) is at least 10% of the maximum diameter or the maximum width of the individual LEDs (10) in the electrode or fence level (19). In the exemplary embodiment, the distance between the center lines (18) of two adjacent luminescent diodes (10) is approximately 150% of the basic size.

A multi-part is used for the injection molding of the LEDs (10)

Form (61-63) used, which together with the spray nozzle (71) specifies the shape of the luminescent diode (10). The majority of the diode (10) to be manufactured is encompassed by a slide shape (62). The latter forms, for example, a seamless main light exit surface and the part of the peripheral surfaces of the electronics protection zone (41) which faces away from an adjacent basic shape (61). With the exception of a suction channel (66) and the spray nozzle system, the base area (42) and the remaining peripheral surfaces of the LED (10) are closed by the basic shape (61) and a lifting shape (63), e.g. A throttle slide (31) is integrated in the basic shape (61) according to FIGS. 3 to 8.

The basic form (61) is e.g. one of the basic elements of the injection mold. It is attached to the stationary part of the tool and is not moved during demolding. It has a recess (73) into which the spray nozzle (71) projects in a sealing manner.

According to FIGS. 3 to 8, a throttle slide (31) is inserted into a rectangular channel (91) for each mold cavity (60) in the base frame (61). The throttle slide (31) are connected to one another in their rear areas via webs, cf. FIGS. 5 and 8. The direction of movement of the throttle slide (31) is oriented, for example, parallel to the base area (42) of the LED (10) and normal to the electrode fence (80). In relation to the luminescent diode (10) is the top of the respective free end of a throttle valve (31) on or just below the chip level (7).

Depending on the space available in the mold (61-63), the throttle slide (31) with the electrode fence level (19) can also form an angle of 5 to 45 °. Possibly. the throttle slide (31) can also be moved by swiveling or screwing within the mold (61-63).

The end of the throttle slide (31) projecting into the cavity (60) is referred to as the shaped element (32). Its end face facing the LED center line (18) is e.g. a curved spatial surface (33) which corresponds exactly to the cut surface which arises in a spatial cut between the truncated cone (14) and the channel (91), i.e. the curvature corresponds to that of the conical surface of the outer surface (14). The shaped element (32) has a trapezoidal cross section in the plane of the drawing in FIG. 3, that is to say in longitudinal section. The shear of the trapezoidal cross section with respect to the LED center line (18) corresponds here to the truncated cone angle of the truncated cone (14). In the horizontal top view, cf. Figure 5 below, the surface of the molded element (32) protruding into the cavity (60) is shown hatched. The curved border of this surface (34) oriented towards the LED center line (18) represents the upper edge (36) as an arc section.

This upper edge (36), which is also the front edge of the molded element (26, 28 32), can assume any curvature, even not flat. It can also be equipped with a structure that influences the flow and projects into the volume flow. The structure can be a corrugation, a wave profile, a knob structure or the like. In the exemplary embodiment according to FIGS. 3 and 7, the throttle slide (31) adjoins the slide shape (62) in some areas.

In FIG. 1, a projection (26) protrudes into the cavity (60) instead of the throttle slide (31). The projection (26) is part of the basic shape (61). The longitudinal section contour (35) of this projection or shaped element closes with the LED center line (18) e.g. a 24 ° angle.

According to FIG. 3, the stroke shape (63) is arranged opposite the base shape (61). According to this illustration, the latter is moved to the right away from the basic shape (61) for demolding. When the mold (61-63) is closed, the molded parts (61) and (63) touch in a parting line (65) shown in FIG. The parting line (65) divides in the area between the electrodes (1, 4) to form an opening (67). The opening (67) is an edge of the suction channel (66) touching the bottom region (42), cf. Figure 3. The suction channel (66) is offset by several tenths of a millimeter from the electrode plane (19) - away from the spray nozzle (71).

A hold-down device (69) is arranged in the lifting form (63). The hold-down device (69) can be moved - e.g. towards the opening stroke of the mold - stored there. He clamps the electrode fence (80) against the basic shape (61).

On the plane formed by the molded parts (61, 63), on which the future bottom area (42) of the LED (10) rests, and on the contour of the basic shape (61) surrounding the spray nozzle (71), the slide shape ( 62). A spatially graduated parting line (64) lies between the slide form (62) and the base form (61). The slide mold (62), which surrounds the majority of the future LED surface, is crossed by at least one temperature control channel (68) in order to temper the mold and the other tool parts surrounding it, for example by means of water or oil at, for example, 40-160 ° C. , In Figure 3, the carriage shape (62) is shown only as an example from one part. In the event that the diode-shaping part is seated within the carriage shape (62) in a separate carriage carrier, the latter can also be equipped with the temperature control channel. According to FIG. 2, the carriage shape (62) may have a projection (28). Its upper edge is also on or below the chip level (7).

The mold (61-63) is open to prepare for injection molding. For this purpose, the molded parts (63, 69), according to FIG. 3, are pulled off to the right. The carriage shape (62) is moved obliquely to the right at the top right by means of a guide, not shown, at an angle of, for example, 25 ° with respect to the spray nozzle center line (75). The electrode fence (80) equipped with the chips (6) and the corresponding bonding wires (2) is inserted and centered on the base shape via index pins (not shown). To close the mold (61-63), the lifting mold (63) moves towards the basic mold (61). The hold-down device (69) stored in it continues in the closing direction until the electrode fence (80) is clamped onto the base mold (61). For example, the slide shape (62) moves towards the shapes (61) and (63) at the same time. The throttle slide (31) is now inserted into the cavity (60) to such an extent that the cross-sectional area (30), shown in dashed lines in FIG. 5, of the narrowest point between the electrode fence (80) has reached its minimum. The reduction in cross-section can amount to 20 - 80% of the original cross-section. The cavity of the mold (61-63) to be sprayed with flowable material is evacuated via the suction channel (66) and, for example, via the gap between the lifting mold (63) and the hold-down device (69). The vacuum is maintained throughout the injection molding process.

Immediately after the evacuation, the hot, flowable material (8) or (9) is sprayed through the respective spray nozzle (71), e.g. a so-called torpedo nozzle, inserted into the corresponding cavity of the mold (61-63). The center line (75) of the spray nozzle (71) and the jet emerging from it is oriented normal to the electrode plane (19). It lies between the bottom area (42) and the lowest point of the reflector trough (5). In the exemplary embodiment, the center line (75) is at half the height of the cylinder (11). It runs centrally between the electrodes (1, 4), cf. Figures 5 and 8.

According to FIG. 2, the liquid plastic (8), for example an injectable transparent, possibly colored thermoplastic, such as modified polymethyl methacrylimide (PMMI), shoots into the evacuated, tempered mold during the injection molding process with a pressure of 700 ± 300 bar ( 61-63) a. The inflow speed is, for example, 0.2 to 10 millimeters per second. The beam passes the electrodes (1, 4), which are offset to the insertion point (70) - offset by a distance calculated from the difference between the clear distance (86) and the distance (85) - and divides at the insertion point (70) opposite wall of the form (62). The beam loses so much energy that the inflowing plastic when filling the cavity, cf. Figure 1, in front of and behind the electrode plane (19) flows from the bottom up. The throttling of the volume flow generated by the projection (28) forces an approximately equally large amount in front of and behind the electrode fence (80). hike up the flow front (92-95). Between the positions (94) and (95) of the flow front, the fast flowing material (8) reaches the bonding wire (2) in front of and behind the electrode fence (80) simultaneously and with a flow direction that runs parallel to the LED center line (18). The bonding wire (2) is flowed around without changing its prescribed position. The bond wire (2) is neither pushed to the side nor torn off.

If the material (8) or (9) is introduced into a mold in which the electrodes (1, 4) or the electrode plane (19) are further away from the insertion point or is than 35% of the space between the mold sides (78) and (79) located distance (86), e.g. in the case of a central position within the mold (61-63), molded elements (26, 32) are used to throttle the volume flow, which are located directly above the insertion point (70), cf. Figures 1, 3 and 7. Here the material (8, 9) jams in front of the electrode fence (80) and pushes up there - without a corresponding shaped element (26, 28) - faster than behind the fence (80). When using the shaped elements (26, 32), the respective material (8, 9) pushes past the chip (6) almost simultaneously, at least in the area of the bonding wire (2). Even with this flow around the chip, the optimal position of the bonding wire (2) is not changed.

In the device according to FIGS. 3-8, after the mold has been completely pre-filled, the material pressure is maintained and the throttle slide (31) is pulled back to the outer contour (14) of the LED (10). This fills the space released by the throttle slide (31).

After the injection molding and the demolding, the webs (81) between the luminescence diodes (10) and the electrodes (1, 4) of the individual LEDs (10) are removed, for example by stamping, in a separating process. Reference symbol list:

1 connection, anode, electrode

2 bond wire, aluminum wire 4 connection, cathode, electrode

5 reflector pan

6 chip

7 chip level

8 Material, thermoplastic 9 Material, thermoset, epoxy resin

10 LEDs, luminescent diode, diode

11 cylinders, flange-like collar 12, 13 flats

14 truncated cone, outer contour

15 calotte

16 Impression of the injection molding nozzle

18 LED center lines, LED longitudinal axes

19 electrode level, fence level

20 LED bodies 21 light guide bodies

22 1st flow front to (26)

23 2nd flow front to (26)

24 3rd flow front to (26)

25 4th flow front to (26) 26 projection, molded element to (61)

28 projection, molded element on (63) Cross-sectional constriction, throttling point, cross-sectional area slide, throttle slide molded element, surface area, curved molded element surface that protrudes into (60) Contour, longitudinal cut contour upper edge

Parting line between (61) and (31) Parting line, fictional between (21) and (41)

Electronics protection zone floor area

Mold cavity, basic form, slide form, stroke form, parting line between (61) and (62) parting line between (61) and (63) suction channel opening, temperature control channel hold-down device

Feed point for material (8, 9) spray nozzles, torpedo nozzles, hot runner nozzles, heating cartridges, recess in (61) 75 center lines of the spray nozzles

78 Mold side on which the spray nozzle (71) lies

79 mold side opposite the spray nozzle (71)

80 electrode fence (leadframe strips), even

81 bridges, upper

85 Distance between (70) and (81)

86 distance between (70) and (79) in the region of the collar (11)

91 channel

92 1st flow front to (28)

93 2nd flow front to (28)

94 3rd flow front to (28)

95 4th flow front to (28)

Claims

Claims:

1. A method for producing light-guiding LED bodies (20) from a material which is flowable before the final solidification by introducing them into a mold (61-63), the individual LED body (20) having at least one light-emitting chip (6) and comprises at least two electrodes (1, 4), which are electrically connected to the chip (6), and the flowable material between a bottom region (42) of the shape (61-63) and the chip (6) at least approximately parallel to the chip plane (7 ) and is injected at least approximately normal to a plane (19) formed by two electrodes (1, 4) between the electrodes (1, 4), characterized in that

- That the volume flow of a flowable material (8, 9) - at a distance (85) of the electrode plane (19) from the

Insertion point (70) that is greater than 35% of the distance (86) between the insertion point (70) and the mold side (79) opposite the insertion point (70) of the mold (61-63) - above the insertion point (70) and below the chip level (7) on the mold side (78) of the insertion point (70) is throttled by at least one cross-sectional constriction (30), while - at a distance (85) that is less than or equal to 35% of the distance (86) - The throttling takes place on the mold side (79) opposite the introduction point (70).

2. Manufacturing method according to claim 1, characterized in that the cross-sectional constriction (30) is produced by at least one shaped element (26, 28, 32) projecting into the cavity (60) of the mold (61-63).

3. Manufacturing method according to claim 1, characterized in that the shaped element (32) is part of a slide (31) which moves into the cavity (60) of the mold (61-63) before the flowable material (8, 9) is introduced becomes.

4. Manufacturing method according to claim 3, characterized in that after a pre-filling of the shape by the shaped element (32) volumetrically reduced shape of the slide (31) for the final filling of the shape (61-63) with that of the LED center line (18) facing room surface (33) of the molded element (32) is at least partially moved back to or behind the outer contour (14) of the luminescence diode (10) there.

5. Manufacturing method according to claim 3, characterized in that the slide (31) inserted before the introduction of the flowable material (8, 9) during the introduction is continuously moved back - over the entire filling process.

6. The device for the production method according to claim 2, characterized in that the cross-sectional constriction (30) is produced by a shaped element (26, 28, 32) projecting into the shape in a wedge-like manner, as seen in the longitudinal section of the luminescent diode (10).

7. The device for the production method according to claim 2, characterized in that the contour (35) shown in longitudinal section of the space surface (33) facing the LED center line (18) with the LED center line (18) forms an angle of 5 to 45 Includes degrees of angle, the intersection between the extension of the contour (35) and the LED center line (18) above the chip plane (7).

8. The device for the production method according to claim 2, characterized in that the cross-sectional constriction (30) is produced by a shaped element (26, 28, 32), seen in cross-section through the luminescent diode (10), in the form of a sickle or annular piece.

9. Device for the manufacturing method according to claim 2, characterized in that the surface area (33) of the molded element (32) facing the LED center line (18) is a jacket part of the outer contour (14) of the luminescence diode (10).

10. The device for the production method according to claim 2, characterized in that the point of the upper edge (36) of the molding element (26, 28, 32) that comes closest to the LED center line (18) on or below the chip level (7 ) lies.